(a) Field of the Invention
The present invention relates to a fuel cell system. More particularly, the present invention relates to a hydrogen generator that can generate hydrogen gas through a hydrolysis reaction of sodium borohydride (NaBH4).
(b) Description of the Related Art
As is well known, a fuel cell is an electric generator that can generate electrical energy using a fuel and oxidizing gas.
Fuel cells may be classified into polymer electrolyte membrane fuel cells and direct oxidation membrane fuel cells. The polymer electrolyte membrane fuel cell is configured to generate electrical energy through an electrochemical reaction between hydrogen gas and an oxidizing gas supplied separately.
It is well known that hydrogen gas is generated by a chemical reaction. For example, a hydrolysis reaction of a fuel such as sodium borohydride (NaBH4) has been widely used to generate the hydrogen gas.
A first conventional hydrogen generator for generating the hydrogen gas using the hydrolysis reaction of sodium borohydride (NaBH4) has a structure where catalysts are added to a fuel solution that is a mixture of sodium borohydride and water. A second conventional hydrogen generator has a structure wherein the fuel and water are supplied into a reaction container in which the catalysts are received. A third conventional hydrogen generator has a structure wherein a catalytic solution is supplied into a reaction container in which solid sodium borohydride is received.
In the first conventional hydrogen generator, since the catalysts are added to a fuel solution that is a mixture of sodium borohydride and water, byproducts such as sodium metaborate (NaBO2) having a relatively high viscosity are produced in the fuel solution. Therefore, the fuel utilization efficiency is lowered due to the byproducts. Further, it is difficult to control the hydrogen generation speed.
In the second and third conventional hydrogen generators, since the fuel and water are supplied into the reaction container in which the catalysts are received or the catalytic solution is supplied into the reaction container in which solid sodium borohydride is received, when the water discharged from the fuel cell is reused by being supplied to the reaction container, the concentration of the fuel or the concentration of the catalysts varies by the reused water as time passes.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.